Study Groups


Resizing and Cropping for PTD Study Groups

Preparing Digital Images

The procedures and techniques described herein are intended to provide a means of modifying digital images for use in projection situations. This includes images being displayed on a screen (using a projector) or on a computer monitor. 

These techniques may be used with both Photoshop and Photoshop Elements post-processing software. (Note: Elements does require an extra step to get started in Sizing – select Image, then Resize and finally Image Size.) 

It is best to perform the steps described below on Photoshop (.PSD) files to preserve image quality. To create a PSD version of the original file, simple use the File>Save As command and select PSD as the file type. The steps may also be applied directly to JPEG/JPG files. 

The term cropping, as used within these techniques, is intended to mean that selected outer portions of the original image are removed and discarded. This will affect the dimensions and, in turn, the file's size. Sizing, by contrast, as used herein, relates to the adjustment of the file's dimensions, without altering its content. A change in the dimensions, either by cropping or sizing, will affect the image's file size. In the normal work flow of post-processing a digital image, it is best to perform cropping before sizing. The only exception to this would be that the original composition of the image is acceptable and desirable. 

It should be noted that a few of the steps described below contain instructions relating to PC operating systems. Accordingly, it will be necessary to make the appropriate adjustments for MAC computers.  


Cropping an Image

The primary purpose of cropping is to improve the composition of an image, if it cannot be done in-camera. Frequently, this is accomplished by removing offending or unnecessary elements, or parts thereof. Another result may be the removal of part of the original image so that the location of key elements is optimized. 

The following contains a sequence of steps, with explanations, that can be taken when cropping a digital image that is to be projected either on a screen or a computer monitor. They are applicable to both Photoshop (*.PSD) and JPEG/JPG files. 

Step 1 - Create a Photoshop (.PSD) file.  Note: This step may be skipped if you are working with a JPEG/JPG file. 

If you have not done so already, it is best to save a copy of the original image as a Photoshop file. To perform this step, click on File, then Save As, then Photoshop (.PSD) in the Format window. This will create a PSD version of the original file and open it for processing. 

JPEG/JPG files are of a compression type and each operation performed on them may cause a slight degradation in the image's quality. This loss of quality does not occur when altering a PSD file. 

Step 2 - Maximize the image. 

If the opened image is still encased in a frame, it is best to maximize the image. By clicking on the Maximize box, located near the upper right corner of the frame, it will be removed and maximum unencumbered access to the image will be available. It is also best to enlarge the image (use Zoom Tool) to the maximum size that almost but not quite fills your monitor. This will give you the best vision. 

Step 3 - Select the Crop Tool. 

The Crop Tool is located in the Tool Box. Its exact position varies, depending upon the post-processing software (Photoshop or Elements) you are using. After making the selection by clicking on the icon, the icon will also appear on the leftmost side of the third bar down from the top of the screen. 

Step 4 - Clear the Width, Height and Resolution Boxes 

To the right of the Crop Tool icon on the bar described above, there are three boxes labeled (on their left side) Width, Height and Resolution. Before proceeding further, these boxes should be cleared, if necessary. This can be accomplished by deleting their contents. This will provide you with the greatest flexibility when selecting the part of the image to be retained. 

Step 5 - Create the Cropping Frame 

A cropping frame can be created by placing the Crop Tool icon in or near one of the image's corners and then dragging it diagonally to the opposite corner. The resultant cropping frame will have 4 dashed lines, which are parallel to the outer edges of the image. The areas outside the frame will be visibly different (less distinct) from the interior, which will retain its original appearance. In the middle of the 4 dashed lines, there will be small boxes;by selecting these boxes and dragging them, you will be able to get the composition you want. There will be boxes in each of the corners, as well; these will enable you to modify the scene in two directions at once. 

Step 6 - Adjusting the Cropping Frame 

Adjustments may be made to the cropping frame by moving any or all of the lines inward or outward, as deemed appropriate. Two of the sides may be adjusted simultaneously by moving the location of a box which defines a corner. The entire frame may be moved in any direction by clicking anywhere in the interior and dragging it as desired. Adjustments may be continued until the desired composition is achieved. 

Step 7 - Performing the crop

To complete the actual crop, once again click on the Crop Tool icon in the Tool Box. A pop-up window will appear with three choices. Selecting “Don't Crop” will cause the cropping frame to disappear (to start over, go back to Step 5). Clicking on “Cancel” allows adjustments to be continued. Selecting the “Crop” choice will cause the crop to be effected (the cropping frame will disappear). 

Even at this point, an unsatisfactory crop may be cancelled by “stepping backward” in the listing of actions shown in the History window. It would then be necessary to proceed back to Step 6 and try again. 


Sizing an Image

Re-sizing an image is generally performed to alter its dimensions without changing its content. This will also have the effect of altering the image's file size. 

While sizing may be applied directly to an image at anytime, it should always be considered, and most often performed, immediately after cropping. In the course of sizing, it is generally best to set one of the dimensions to the maximum allowable for best viewing. An image with small dimensions is more challenging to view properly and is often enlarged too much by a viewer who is trying to better understand the contents of the scene. When an image is enlarged too much, more than about 110%, some of its elements and features are apt to become distorted.

The following steps, with explanations, permit the sizing of images with the greatest ease and simplicity. They are applicable to both PSD and JPGE/JPG files.

Step 1 - Open the folder.

If this has not been done already, open the folder containing the file to be resized. Further, set the viewing option to Details. This will allow the viewing of the file's size, with just a quick click. 

Step 2 - Open the file. 

If this has not been done already, open the image file to be resized, in Photoshop or Elements, as appropriate. It is not necessary to maximize the file. 

Step 3 - Open the Image Size window. 

In order to perform file sizing, it is necessary that the Image Size window be opened. In Photoshop, this can be accomplished by selecting the Image Size option in the Image drop-down window. For Elements, it is necessary to first select the Resize option in the Image drop-down window, and then select the Image Size option in the second window that is opened. 

There are 3 distinct areas in the Image Size window. At the top, the current Width and Height dimensions are shown. The middle area, among other things, indicates the current resolution of the image. The selections at the bottom are used to control the modification of the dimensions. For example, the Constrain Proportions box should always be checked, for this will cause any adjustment of one dimension to proportionally change the other. 

Step 4 - Change the dimensions. 

It is important that the Constrain Proportions box at bottom of the window be checked before attempting to alter an image dimension, as this ensures that both dimensions are changed simultaneously and proportionally. A dimension size can be changed by entering a value directly into the appropriate box at the top of the window. As has been stated previously, it is best to enter a maximum allowable dimension. However, it is possible to have a resulting Height dimension to be too large when entering the maximum Width value. In such cases, simply change the Height dimension to the maximum allowable and the Width dimension will be adjusted automatically. Also, when reducing the size of a dimension, it is best to have the box to the right of Resample Image to indicate Bicubic Sharper. 

Step 5 - Close the Image Size window. 

To close the Image Size and implement the change, click on the OK button in the upper right corner of the window. The changes are not effected until this is accomplished. The presence of the Cancel button should also be noted. This permits determining the current dimensions and resolution of the image without effecting a change.